Governments in Eastern European transition countries are confronted with comparatively large problems. Therefore, and as far as the stability of a government can be considered one of the prerequisites of its efficiency, this paper analyses the conditions of stable government on the basis of institutional rules and the characteristics of party systems. Empirical evidence is drawn from data on 76 governments in 16 Eastern European member states of the Council of Europe till January 1999. The result is that institutions matter as well as the number of parliamentary parties: On the one hand, institutional rules on investiture, dissolution of parliament, and votes of non-confidence determine the risk of governmental instability, on the other hand fragmented party systems cannot produce stable governments.